A former Broken Ground School teacher has been charged with mailing drugs to state prison inmates who are members of a white supremacist gang.

The police said Peggy Sinclair, 50, conspired with 22-year-old Matthew Peters, her boyfriend, former student and a street captain of the Brotherhood of White Warriors gang, to mail envelopes to the prison containing a prescription drug.

Sinclair has also placed money on the phone cards of gang members in prison and given them credit card numbers that allowed them to access cash, the police said. Her involvement with the gang, called BOWW, began in May 2012, said Concord police Lt. Timothy O’Malley. She is identified in court documents as “one of Peters’ girlfriends who provided financial support to him and to other members of the gang still inside the prison.”

Concord school Superintendent Chris Rath announced Sinclair’s resignation last week in a statement thanking the fifth-grade teacher for her years of service. The new charges are “a big surprise,” Rath said yesterday, “an awful surprise.”

Sinclair’s resignation came after months of paid administrative leave following her arrest in April. A police officer pulled her and Peters over for illegal passing in Canterbury and discovered the smell of marijuana was coming from the car. The police seized the car after the pair did not comply with a search. Prescription pills were found in Sinclair’s purse, and she was charged with possession of prescription drugs. The case against her was dropped two months later, after her attorney presented her valid prescription for the bupropion pills. The police also found marijuana and cocaine in a backpack with Peters’s license.

Peters, who has a criminal history, has since been charged with a February armed robbery that the police said was carried out as retribution for insulting the BOWW gang. He is being held at the state prison in Concord, where two envelopes containing the drug Suboxone were intercepted this spring and traced to Sinclair through her DNA.

Suboxone is the most-common controlled drug to smuggle inside the prison through the mail, according to court documents, because it comes as a thin film that users place under the tongue to absorb into their bloodstream.

The police said Sinclair hid the strips in the mail by cutting a second envelope and hiding it inside to conceal the drug.

The drug is prescribed to help opiate addicts overcome addiction, but “has become an abused drug in its own right,” according to an arrest affidavit, which states that a single Suboxone film sells for as much as $125 inside the state prison.

In calls between Sinclair and Peters while Peters was in prison this spring, the police said the couple referred to Suboxone film with code words like “pictures,” “resumes” and “cameras.”

Peters asked Sinclair in a May 17 phone call whether she mailed him any letters that day, the police said, and she responded that she had to wait for “a certain part of the procedure.” Later that day, she told him she put the letter “right in the postman’s hand,” and investigators used that information to monitor the mail Peters received. That, and another letter sent to inmate Stefan Gauthier, were intercepted with nonexistent return addresses.

The police got a warrant to collect DNA from Sinclair last week, and said that DNA from saliva on the envelopes matched Sinclair’s. One of the envelopes has tested positive for Suboxone and the other is still awaiting testing, the police said.

Prosecutor Tracy Connolly said at Sinclair’s arraignment yesterday that the investigation is ongoing, but the police filed charges because they believed from prison phone calls that Sinclair might have left the state.

She is facing felony charges for two counts of possession of controlled drugs, two counts of conspiracy and two counts of delivery of articles to prisoners. Sinclair is also charged with two Class A misdemeanors for breach of bail conditions, because her April drug charges had not yet been dropped when she allegedly mailed the Suboxone in May and June.

Sinclair, a fifth-grade teacher, taught in Concord for 27 years. Peters appears as one of 25 students in “Mrs. Sinclair’s Class,” according to a 2002-03 Broken Ground School yearbook.

The police said Sinclair, who was married and teaching in Concord when they believe she began her involvement with the gang, gave money to Peters to purchase a vehicle and rent an apartment in Concord. Court documents showed at the time of their arrests in April that the couple was sharing a Highland Street apartment.

In response to a Right-to-Know request from the Monitor regarding Sinclair’s resignation, Rath said the school district had not yet signed an agreement with Sinclair or made payments to the former teacher.

Rath said the statement issued last week announcing Sinclair’s resignation was an agreed-upon statement between the school district and Sinclair. She said she could not make any further comments until she speaks with the school district’s attorney and understands her options.

Sinclair’s attorney, Jared Bedrick, said in court yesterday that his client is divorced and has two children. She has “zero record” of criminal activity, he said, noting that the April drug charges have been dropped. Bedrick told the Monitor in July that Sinclair had expressed surprise when details of Peters’s gang involvement became public.

“It’s way too early” to comment on the new charges against Sinclair, Bedrick said after yesterday’s arraignment.

The investigation of gang activity that led to the most recent charges against Sinclair began in February. The police said the armed robbery that Peters is charged with was part of an attempt by the gang to “build a profitable criminal enterprise outside of the prison walls.” Peters and another gang member are accused of violently attacking a man and trying to steal a large amount of heroin in that February robbery. The police said the victim lost four teeth in the assault.

After that incident, the Concord police, state Department of Corrections and state police began monitoring BOWW’s activity. Prosecutors have said the gang has about 70 active members both inside and outside the prison. BOWW formed in the prison in 2005, uses Nazi symbolism and has become a major source of violence inside prison walls, according to the police.

O’Malley said yesterday that he could not comment on how Sinclair became involved with the gang.

Sinclair turned herself in to the police yesterday morning, and appeared at her arraignment in Concord’s district court dressed in a T-shirt and blue jeans. She was then taken to Merrimack County jail, where she was held yesterday on $32,000 cash bail. Judge Gerard Boyle ordered that she can have no contact with Peters.

She is next scheduled to appear in court Sept. 12 for a probable cause hearing.